This disclosure is related generally to the field of marine surveying. Marine surveying can include, for example, seismic and/or electromagnetic surveying, among others. For example, this disclosure may have applications in marine surveying in which one or more geophysical sources are used to generate energy (e.g., wavefields, pulses, signals), and geophysical sensors—either towed or ocean bottom—receive energy generated by the sources and possibly affected by interaction with subsurface formations. Towed sensors may be disposed on cables referred to as streamers. Some marine surveys locate geophysical sensors on ocean bottom cables or nodes in addition to, or instead of, streamers. The geophysical sensors thereby collect survey data which can be useful in the discovery and/or extraction of hydrocarbons from subsurface formations.
Historically, geophysical sources have been towed at or near the water surface. Flotation and towing systems have positioned the sources vertically (i.e., water depth), laterally (i.e., in the cross-line direction; horizontal and perpendicular to the local towing direction), and axially (i.e., in the in-line direction; horizontal and parallel to the local towing direction). Near-surface towing has provided easy access for power and data transfer. However, deep towing of sources may provide better data quality in many instances. In some instances, surface obstructions impede shallow towing of sources. At times, data may be desired from sources at more than one depth and/or horizontal position. Towing systems may sometimes suffer from vibration or other sources of noise. It would be beneficial to steer sources and/or source arrays in conjunction with and/or independently of existing flotation and towing systems.